U.S. patent application number 15/776641 was filed with the patent office on 2018-11-15 for a method of fabricating an airfoil preform, an airfoil, and a nozzle sector, by selective melting on a bed of powder.
The applicant listed for this patent is SAFRAN AIRCRAFT ENGINES. Invention is credited to Sebastien DREANO.
Application Number | 20180326495 15/776641 |
Document ID | / |
Family ID | 55752367 |
Filed Date | 2018-11-15 |
United States Patent
Application |
20180326495 |
Kind Code |
A1 |
DREANO; Sebastien |
November 15, 2018 |
A METHOD OF FABRICATING AN AIRFOIL PREFORM, AN AIRFOIL, AND A
NOZZLE SECTOR, BY SELECTIVE MELTING ON A BED OF POWDER
Abstract
A method of fabricating an airfoil preform for a turbine engine
by selective melting on a bed of powder, the preform including an
airfoil and a removable support secured to the airfoil, the airfoil
being fabricated layer by layer from a first edge to a second edge
of the airfoil, the method including fabricating the removable
support and the airfoil, the removable support being for securing
to a fabrication platform and to a portion of a face of the airfoil
situated near the first edge and facing the fabrication platform.
The face of the airfoil facing the fabrication platform includes a
flat extending away from the face, the flat being present over a
portion of the face that is situated outside the first edge, the
support being secured to the flat or both to the flat and to the
portion of the face that is situated outside the first edge.
Inventors: |
DREANO; Sebastien;
(LONGJUMEAU, FR) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SAFRAN AIRCRAFT ENGINES |
PARIS |
|
FR |
|
|
Family ID: |
55752367 |
Appl. No.: |
15/776641 |
Filed: |
November 10, 2016 |
PCT Filed: |
November 10, 2016 |
PCT NO: |
PCT/FR2016/052928 |
371 Date: |
May 16, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29C 64/153 20170801;
B23K 2101/001 20180801; F01D 9/044 20130101; B23P 15/04 20130101;
B33Y 80/00 20141201; B22F 2003/1058 20130101; B29C 64/40 20170801;
F01D 5/14 20130101; B22F 5/04 20130101; B22F 5/009 20130101; B23K
26/342 20151001; B22F 2003/247 20130101; F05D 2230/22 20130101;
Y02P 10/295 20151101; F05D 2230/20 20130101; B22F 3/1055 20130101;
Y02P 10/25 20151101; B33Y 10/00 20141201 |
International
Class: |
B22F 5/00 20060101
B22F005/00; B22F 5/04 20060101 B22F005/04; B23K 26/342 20060101
B23K026/342; F01D 9/04 20060101 F01D009/04; F01D 5/14 20060101
F01D005/14; B22F 3/105 20060101 B22F003/105 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 17, 2015 |
FR |
1561021 |
Claims
1. A method of fabricating an airfoil preform for a turbine engine
by selective melting on a bed of powder, the preform comprising an
airfoil and at least one removable support secured to the airfoil,
the airfoil being fabricated layer by layer from a first edge of
the airfoil corresponding to a leading edge or to a trailing edge
of an airfoil to a second edge of the airfoil corresponding to a
trailing edge or a leading edge of the airfoil, the method
comprising fabricating the removable support and the airfoil, said
removable support being for securing firstly to a fabrication
platform and secondly to a portion of a face forming a pressure
side or a suction side of the airfoil situated in the vicinity of
the first edge of the airfoil and facing said fabrication platform;
wherein the face forming a pressure side or a suction side of the
airfoil and facing the fabrication platform includes a flat
extending away from said face, the flat being present over a
portion of said face that is situated outside the first edge of the
airfoil, the removable support being secured to the flat or both to
the flat and to the portion of said face that is situated outside
the first edge.
2. A method according to claim 1, wherein the flat comprises a
first face parallel to the fabrication platform and tangential to
the first edge of the airfoil.
3. A method according to claim 2, wherein the flat further
comprises a second face perpendicular to the first face.
4. A method according to claim 3, wherein a point of the flat at
the intersection between the first and second faces of said flat is
situated at a distance from the face of the airfoil facing the
fabrication platform that is less than or equal to 0.5 mm.
5. A method according to claim 1, wherein the removable support is
a cellular support.
6. A method of fabricating a turbine engine airfoil, further
comprising: fabricating an airfoil preform by a method according to
claim 1; and removing the removable support and the flat from the
airfoil preform.
7. A method according to claim 6, wherein the removing of the
removable support and the flat comprises polishing the airfoil.
8. A method of fabricating a turbine engine nozzle sector by
selective melting on a bed of powder, the nozzle sector comprising
a plurality of stationary airfoils carried by two ring sectors,
wherein the stationary airfoils are fabricated by a method of
fabricating an airfoil according to claim 6.
9. A turbine engine airfoil preform comprising an airfoil and at
least one removable support secured to the airfoil, wherein a face
of the airfoil forming a pressure side or a suction side includes a
flat extending from said face, the flat being present over a
portion of said face situated outside a first edge of the airfoil
corresponding to the leading edge or to the trailing edge of the
airfoil, the removable support being secured to the flat or both to
the flat and to a portion of said face situated outside the first
edge.
10. A preform according to claim 9, wherein the flat has a first
face that is tangential to the first edge of the airfoil and a
second face that is substantially perpendicular to the first face.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to the general field of
additive fabrication methods. The present invention relates more
particularly to a method of fabricating turbine engine airfoils by
selective melting on a bed of powder.
[0002] Nowadays it is common practice and advantageous to have
recourse to additive fabrication techniques for making complex
three-dimensional parts easily and quickly. The field of aviation
is particularly suitable for the use of methods of this type.
[0003] When fabricating parts out of metal or metal alloy, the
method of selective melting on a bed of powder makes it possible to
obtain complex parts that are difficult or impossible to make using
conventional methods such as casting, forging, or machining.
[0004] Such a method typically comprises a step during which a
layer of powder is deposited on a fabrication platform, followed by
a step of selectively melting a portion of the deposited layer of
powder by using a heater member. The above steps are repeated in
succession so as to build up the final part layer by layer.
[0005] FIG. 1 shows a turbine nozzle sector 1 for an aviation
turbine engine comprising a plurality of stationary airfoils 2
extending between two concentric rings 3 and 4 that are arranged on
a horizontal fabrication platform 5. When the nozzle is in such a
configuration, the airfoils 2 are "suspended", i.e. they are
cantilevered out from the rings 3 and 4.
[0006] When it is desired to fabricate such a nozzle sector 1 by
selective melting on a bed of powder, it is necessary during
fabrication to provide removable or breakable supports 6 (see FIG.
1) that hold the airfoils while they are being fabricated.
Specifically, in methods of selective melting on a bed of powder,
it is essential for each melted layer to be capable of being held
up by material that has already previously been melted. Such
supports 6 are inevitably present at the leading edge or the
trailing edge of the airfoils 2 (depending on whether the nozzle
sector is fabricated one way up or the other), and also on a
portion of the faces 2a of the airfoils facing the fabrication
platform 5 (see FIG. 5).
[0007] Nevertheless, the presence of such removable supports at the
leading edge or the trailing edge is not desirable. Specifically,
once the nozzle sector has been fabricated in the tooling for
selective melting on a bed of powder, and then separated from the
fabrication platform, it is necessary to remove the removable
support. A manual polishing step is needed to eliminate the
residues of those supports. During the manual polishing, the
operator needs to move the polishing tool over the edge where the
supports were present (corresponding to the leading edge or the
trailing edge of the airfoil) and to press thereagainst. Manual
polishing can thus lead to shape defects and irregularities for the
edge in question as a result of excessive removal of material. Such
defects may turn out to be problematic for the aerodynamics of the
airfoils during subsequent use in a turbine engine.
OBJECT AND SUMMARY OF THE INVENTION
[0008] A main object of the present invention is thus to mitigate
such drawbacks by proposing a method of fabricating an airfoil
preform for a turbine engine by selective melting on a bed of
powder, the preform comprising an airfoil and at least one
removable support secured to the airfoil, the airfoil being
fabricated layer by layer from a first edge of the airfoil
corresponding to a leading edge or to a trailing edge of an airfoil
to a second edge of the airfoil corresponding to a trailing edge or
a leading edge of the airfoil, the method comprising fabricating
the removable support and the airfoil, said removable support being
for securing firstly to a fabrication platform and secondly to a
portion of a face forming a pressure side or a suction side of the
airfoil situated in the vicinity of the first edge of the airfoil
and facing said fabrication platform.
[0009] In accordance with the invention, the face forming a
pressure side or a suction side of the airfoil and facing the
fabrication platform includes a flat extending away from said face,
the flat being present over a portion of said face that is situated
outside the first edge of the airfoil, the removable support being
secured to the flat or both to the flat and to the portion of said
face that is situated outside the first edge.
[0010] The method of the invention is remarkable in that during
fabrication of the airfoil preform, the method incorporates
fabricating a flat at the first edge of the airfoil (which first
edge may correspond to a leading edge or to a trailing edge
depending on the orientation of the airfoil in the tooling for
selective melting on a bed of powder). The presence of this flat
advantageously enables the portion of the airfoil to which the
removable support is attached to be spaced apart from the first
edge under consideration. In other words, the removable support is
set back from the first edge of the airfoil. When the removable
support is subsequently removed in order to obtain the airfoil,
residue of the support is located on the flat and possibly on a
portion of the face of the airfoil that faces the fabrication
platform, but not directly on the first edge. Thus, when polishing
the airfoil in order to remove the residue, the operator need no
longer press against the first edge of the airfoil, but rather on
the flat and on the face of the airfoil in the vicinity of which
the flat is present. Such a configuration thus serves to limit the
appearance of defects due to removing supports by ensuring that the
airfoil is polished in uniform and controlled manner. In addition,
the time required for adjusting or polishing the airfoil is reduced
by such a technique, by making this step more systematic.
Naturally, techniques other than polishing could be used for
adjusting the shape of the airfoil after the supports have been
removed.
[0011] Preferably, the flat comprises a first face parallel to the
fabrication platform and tangential to the first edge of the
airfoil. For example, the first face may form an angle that is less
than or equal to 5.degree. relative to the fabrication platform.
Since the part is built up layer by layer, each layer being
parallel to the fabrication platform, this means that the first
layer forming the airfoil presents an area, e.g. a rectangular
area. It is advantageous for the first layer to be an area rather
than a line in order to provide better holding of the airfoil, in
particular at its first edge.
[0012] Also preferably, the flat further comprises a second face
perpendicular to the first face. For example, the second face may
form an angle lying in the range 85.degree. to 95.degree. relative
to the first face. Under such circumstances, a point of the flat at
the intersection between the first and second faces of said flat
may be situated at a distance from the face of the airfoil facing
the fabrication platform that is less than or equal to 0.5
millimeters (mm), e.g. less than or equal to 0.3 mm. More
generally, the flat may be integrated in the airfoil in such a
manner that it does not exceed the acceptable level of shape
defects for the airfoil (as set out in specifications, for
example), or in other words, for it to comply with the requirements
for the shape of the airfoil. Thus, when the flat is constructed in
this way its dimensions are smaller than the dimensions of an
acceptable shape defect for the airfoil, so removing it
subsequently, e.g. by machining, can become optional.
[0013] The removable support may be a cellular support.
[0014] The invention also provides a method of fabricating a
turbine engine airfoil, the method comprising the following steps:
[0015] fabricating an airfoil preform by a method as described
above; and [0016] removing the removable support and the flat from
the airfoil preform.
[0017] Preferably, removing the removable support and the flat
comprises polishing the airfoil.
[0018] The invention also provides a method of fabricating a
turbine engine nozzle sector by selective melting on a bed of
powder, the nozzle sector comprising a plurality of stationary
airfoils carried by two ring sectors, the stationary airfoils being
fabricated by an airfoil fabrication method as described above.
[0019] Finally, the invention provides a turbine engine airfoil
preform comprising an airfoil and at least one removable support
secured to the airfoil, one of the faces of the airfoil forming a
pressure side or a suction side including a flat extending from
said face, the flat being present over a portion of said face
situated outside a first edge of the airfoil corresponding to the
leading edge or to the trailing edge of the airfoil, the removable
support being secured to the flat or both to the flat and to a
portion of said face situated outside the first edge.
[0020] Preferably, the flat has a first face that is tangential to
the first edge of the airfoil and a second face that is
substantially perpendicular to the first face.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] Other characteristics and advantages of the present
invention appear from the following description made with reference
to the accompanying drawings. In the figures:
[0022] FIG. 1 is a perspective view of a nozzle sector suitable for
being fabricated by a method of the invention;
[0023] FIG. 2 is a flow chart showing the main steps of a method of
the invention for fabricating an airfoil;
[0024] FIG. 3 is a diagrammatic section view of tooling for
selective melting on a bed of powder in which a nozzle sector is
fabricated;
[0025] FIG. 4 is a detail view of FIG. 3 at the first edge of an
airfoil together with its removable support; and
[0026] FIG. 5 is a view similar to the view of FIG. 3, showing a
prior art method.
DETAILED DESCRIPTION OF THE INVENTION
[0027] FIG. 1 shows a nozzle sector 1 or guide vane set of a
turbine for an aviation turbine engine, as described above. Such a
nozzle sector 1 may be fabricated by a method of the invention by
selective melting on a bed of powder. A step of the fabrication
method includes fabricating airfoils 2 of the nozzle sector 1 (i.e.
its vanes). It should be observed that the invention applies to
airfoils for turbine engines equally well whether the engines are
terrestrial or for aviation.
[0028] A method of the invention for fabricating an airfoil 2 is
described below with reference to the flow chart of FIG. 2 and the
tooling for selective melting shown in FIGS. 3 and 4. Such a method
comprises initially fabricating an airfoil preform (step E1), and
then removing (step 2) the removable support 6 from the preform in
order to obtain the airfoil. The support 6 is thus said to be
"removable" since it is designed to be removed from the airfoil 2
after it has been fabricated by a method of the invention.
[0029] FIG. 3 shows tooling 10 for selective melting on a bed of
powder suitable for use in fabricating a nozzle sector 1 having a
plurality of stationary airfoils 2. For simplification purposes,
the tooling 10 is shown in section during fabrication of a nozzle
sector 1 that comprises only two airfoils 2.
[0030] In known manner, the tooling 10 has a supply of powder 12
and a fabrication zone 14 in which the nozzle sector 1 is
fabricated. The supply of powder 12 contains the metal powder 16 or
metal alloy powder that is to be used for fabricating the nozzle
sector 1, while the zone 14 is suitable for containing the nozzle
sector 1 once it has been fabricated, together with the powder 18
that has not been melted.
[0031] At the bottom of the powder supply 12 there is a platform 20
suitable for moving vertically in order to deliver powder to a
scraper or roller 22 that can subsequently push the powder to the
fabrication zone 14 so as to a form a layer of powder. At the
bottom of the fabrication zone 14 there is a fabrication platform 5
suitable for moving vertically progressively as the nozzle sector 1
is fabricated. The scraper or roller 22 constituting powder
spreader means serves to deposit a layer of powder on the
fabrication platform 5.
[0032] Finally, the tooling 10 includes a heater member 23 having a
generator portion 24 for generating a laser beam or an electron
beam, and a control portion 25 for controlling the path followed by
the generated beam so as to melt selectively a layer of powder
deposited on the fabrication zone 14.
[0033] For each airfoil 2, provision is made to fabricate a
removable support 6 that is secured firstly to the fabrication
platform 5 and secondly to the airfoil 2, thereby enabling the
airfoil 2 to be held throughout the fabrication method. An airfoil
preform is thus fabricated that comprises an airfoil 2 and its
removable support 6.
[0034] FIG. 4 is an enlarged diagrammatic view of an airfoil
preform in the fabrication zone 14 in the vicinity of the removable
support 6. In this example the airfoil preform is fabricated in the
direction indicated by arrow 26. The fabrication of the airfoil
preform begins with the support 6, followed by fabricating the
airfoil 2, beginning with a first edge 28 thereof (corresponding to
the trailing edge of the airfoil in this example) and continuing to
a second edge thereof (corresponding in this example to the leading
edge of the airfoil, not shown). As can be seen in the figures, the
first edge 28 is situated facing the fabrication platform 5, while
the second edge is situated remote from the fabrication platform 5.
In addition, the first edge 28 and the second edge are generally
parallel to the top surface of the fabrication platform.
[0035] In accordance with the invention, a flat 30 is formed on the
airfoil 2, and more precisely on a face 2a of the airfoil and at
the first edge 28 of the airfoil. This flat 30 extends from the
vicinity of the first edge 28 and away from the first edge 28
beside the face 2a of the airfoil that faces the fabrication
platform 5 (in this example this face is the suction side of the
airfoil). In the example shown, the flat 30 has a first face 30a
substantially parallel to the fabrication platform 5 and tangential
to the first edge 28 of the airfoil, and a second face 30b
substantially perpendicular to the first face 30a. In this
configuration, a point 30c situated at the intersection between the
two faces is at a distance d from the face 2a of the airfoil. This
distance d is preferably less than or equal to 0.5 mm, or indeed
less than or equal to 0.3 mm, in order to comply with the
acceptable level of shape defects for the airfoil 2. In general,
the distance d may be selected to be less than or equal to the
acceptable level of shape defects for the airfoil 2, where the
shape defect is generally defined by specifications.
[0036] In this example, the removable support 6 comprises a
plurality of ridges 6a (or tabs) for supporting the airfoil 2.
These ridges 6a are secured on a portion of the airfoil 2 that
extends from the flat 30 to the face 2a of the airfoil and in a
direction going away from the first face 28. The ridges 6a may be
secured to the flat and set back from the first edge 28 of the
airfoil, i.e. the ridges 6a are not positioned exactly at the first
edge of the airfoil but are spaced apart therefrom. In an
embodiment that is not shown, the ridges 6a may be secured on a
portion extending from the middle of the face 30a of the flat 30
and as far as the face 2a of the airfoil.
[0037] It should be observed that, at the end of step E1, the
support 6, the flat 30, and the airfoil 2 form a single part
(referred to herein as the airfoil "preform").
[0038] The removable support 6 is preferably of cellular type. In
general manner, the removable support 6 need not be solid, for
example it may be hollow. This avoids consuming too much material
during the fabrication method, since the support 6 ends up being
removed from the airfoil preform.
[0039] Dashed line 32 in FIG. 4 represents the first layer
constituting the airfoil, and it can be seen that the melted
portion of this first layer that begins fabrication of the airfoil
2 forms a plane as a result of the presence of the flat 30.
Obtaining a first airfoil layer that is constituted by a plane is
advantageous. Specifically, in additive fabrication, in order to
minimize fabrication defects, it is appropriate to avoid as much as
possible beginning a part by melting a single line. Furthermore, by
beginning the fabrication of the airfoil 2 with a plane, it is held
better by the support 6.
[0040] Once the airfoil preform has been fabricated (or a plurality
of preforms for a nozzle or a guide vane set), the removable
support 6 can be removed by cutting through the ridges 6a (step
E2). The residues of the ridges 6a of the support 6 that remain
together with the flat 30 are subsequently eliminated, e.g. using a
polishing tool of the grinder type. The presence of the flat 30
makes it possible to avoid resting the polishing tool against the
first edge 28 during this step. Specifically, it is possible
instead to position the polishing tool against the flat 30 and at
the face 2a so as to avoid damaging the first edge 28. Furthermore,
it is found to be easier to press the polishing tool against the
face 2a instead of against the first edge 28. The presence of the
flat then makes it possible to obtain airfoils having first edges
28 that are regular and that do not present defects greater than
defects that are acceptable as defined by specifications.
[0041] It should be observed that it would not go beyond the ambit
of the invention for a plurality of supports 6 to be used for
supporting an airfoil 2.
[0042] By way of comparison, the positioning of a removable support
6 as may be done in the prior art is shown in FIG. 5. In that
configuration, at least one ridge 6a of the support 6 is positioned
at the first edge 28 in order to be able to hold the airfoil
correctly while it is being fabricated. In addition, the first
layer forming the airfoil 2 (represented by dashed line 32) is
constituted by a line, which is not desirable for the reasons
mentioned above. After the support 6 has been cut away, at least
some residue of ridges 6a is inevitably positioned at the first
edge 28. The presence of this residue makes the steps of adjusting
and polishing the airfoil more difficult, and can lead to defects
at the edge and to irregularity in the set of airfoils 2 as
fabricated.
* * * * *